AtomicGeo

SS109

Yep, like rodrigeo said, they are called hybrids. Over at KDXrider.net we have a sub-forum just for hybrid builds. Mainly KX versions but there have been some CR's and at least YZ hybrid using the KDX200/220 engines. I plan on doing one myself only using the KDX250 engine in a KX or YZ chassis!

Tedh98

My personal opinion would be to just a kx125 suspension on the kdx frame. Yes I know the kx frame is a lot better and more compact but it just seems like a huge task to me.

Putting KX forks on a KDX is a common modification and isn't too much work. But trying to put a KX rear suspension on a KDX would be no easy task. I think it would be pretty tough to get the new mounting locations configured properly so the shock,linkage and swingarm function correctly.

It really isn't that difficult putting the KDX engine in a KX frame. Enough people have done them that most 'problems' have been figured out.

Frankenschwinn

It really is very simple if you have any fabricating experience and mechanical ability. As stated, there are quite a few build guides on here and kdxrider.net. Adding the rear suspension from a KX would be much more work for less gain. the KX chassis handles so much better and feels quite a bit lighter too. some drawbacks include: Harder to work on carb. Smaller fuel capacity. I ended up with a few one off fabbed parts. The end product is so much better though. Not as snappy as a ktm200 but equally fast and light. I personally like the handling better too.

juliend

My personal opinion would be to just a kx125 suspension on the kdx frame. Yes I know the kx frame is a lot better and more compact but it just seems like a huge task to me.

Your personal opinion is wrong in this instance. The engine swap is easier, and more functional. It's been done, and done, and done. There is enough info on the web these days, and even step by step picture threads, to make it a very easy swap.

2strokeDude

Yeah I guess you guys are right. I mean Jeff Fredette Did prove that they are great bikes for offroad racing. I think they could be better than the ktm 200's, especially if you have it in a KX frame as far as the handling goes.

SS109

Now THAT will be a sweet ride! I have always wanted an uncorked and properly tuned KDX250 engine in a modern chassis, that's a very sweet engine. Good luck with it!

Not to hijack the thread but...

Yeah, I picked up the KDX250 because it was such a steal ($450) as something my son could ride and keep around as a buddy bike once he gets his WR250. I have read a lot of negatives about them but I figured it was good for my purposes. Only problem is that I really love the power this engine makes! The chassis, well, not as much. I think the KDX250 engine is perfect for a hybrid build. Who knows, a KDX250-KX might actually demote my 200 to buddy bike status!